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dokeun August 31, 2010 07:53

DPM injection model selection
1 Attachment(s)
I want to modeling water injection with dpm.
now i'm wondering what kind of injection type should be applied for my problem.
Before the work, I solved continuum problem to get velocity and mass flow rate of water injected to refer(see the picture attached)
In this result water is injected from a nozzle to -y direction with swirl.
What kind of injection type is proper for my job? and How can I utilize pre-study result for my work?
Uing UDF for initializing DPM can be a solution?
thank you in advance.

xrs333 August 31, 2010 09:43

Hi, Dokeun,
You mean using DPM to model the atomizing process -- the process of water flows at a high velocity into the media from inside the nozzle and the subsequently breaks up, do you?
No! You'll get nowhere.
The DPM is just a model that tracks the trajectory of discrete particles using Lagrandian representation. The injections are used as the initial conditions for the integral calculation of the trajectory. Among others, the atomizers in the DPM of FLUENT are all emperical models and cannot be used to model the atomizing process. Further more, we may understand the logic in the sense of semasiology -- we cannot use atomizer model to simulate the atomizing process intrinsically.

dokeun August 31, 2010 19:53

Dear xrs333
I appriciate for your kind response.
Due to my poor english, there may be a misunderstanding.
Actually I did not intend to make the break up process of water jet from continuum.
The reason I calculated the continuum problem preliminary is that I wanted to get initial properties(velocity, mass flow rate) at the outlet of nozzle for DPM problem.
As you can see on the picture above, water is injected to outside of nozzle with swirl.
Now I want to set up DPM at the surface(outlet) of nozzle, but I don't know how I can represent the swirl among the injection types.
If the swirl were not for, I could use surface injection for DPM at the surface(outlet) of nozzle.

jump September 1, 2010 00:33

hi, dokeun

I like this topic, and I am very interested in your results.
Regarding the water distribution methods, I think there are two types, "High pressure loss distributor"(like fine screen nozzle) and "Low pressure loss distributor".

What's solid particle in your system? How big?


dokeun September 6, 2010 03:21

Though I'm curious about the break up mechanism from continuum fluid flow, but not this time.

I think i find an extemporaneous way for solving my problem not for your concern.. sorry

The problem I concerned in this post was, so to speak, how to set up the wall jet boundary condition.

I made swirling of water parcels by interacting walls boundry with parcels.

Of course the initial condition(velocities...) of DPM came from results of inter nozzle problem.

dokeun September 6, 2010 03:27

1 Attachment(s)
this is my result.

there are 4 injection walls instead of 1 normal direction nozzle exit.

interaction between the cylinderical wall + screw walls and DPM injection parcels..

thank you any way~

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